I have two ferrets, a young-ish male (Max) and an elderly female (Tilly). Unfortunately, as a full-time university student I don't have much time to take them out of the cage anymore. My house does not allow for free roaming so we need to block off the main hallway whenever we take them out of the cage. Also, due to some unfortunate dryer accidents both of their hammocks are broken. I also had to take the bed out of the cage because Tilly wouldn't stop trying to eat it (she was pulling off massive amounts of fibres). Needless to say, the cage is basically back to its bare bones...

They have:
-2 towels
-1 hanging crinkle tube
-1 cardboard box
-1 hanging parrot toy (that they don't play with)
-1 bell ball (that they don't play with)

The entire bottom half of the cage is litter boxes because someone *coughMaxcough* prefers to use the cage floor.

I'll try to get a new hammock but my mom might insist on fixing the broken ones and then never do it.

What kind of items can I put in the cage to make it more interesting for them in there?